Climate Change Report: Weather Extremes Increasing

In carefully negotiated language worked out among scientists from many countries, a new report on the effects of a warming climate on the world’s weather by the U.N.-sponsored Intergovernmental Panel on Climate Change (IPCC) says that much of the world is already seeing more weather “extremes” – stronger hurricanes and more intense heat waves – at least partly because of the buildup of greenhouse gases in the atmosphere.

The report is called “Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation” — shortened to “SREX.” A draft summary was obtained by ABC News.

A sampling of lines from it:

On temperatures: “It is very likely that there has been an overall decrease in the number of cold days and nights, and an overall increase in the number of warm days and nights, on the global scale, i.e., for most land areas with sufficient data.”

On whether human beings are contributing to the change: “It is likely that anthropogenic influences have led to warming of extreme daily minimum and maximum temperatures on the global scale. There is medium confidence that anthropogenic influences have contributed to intensification of extreme precipitation on the global scale. It is likely that there has been an anthropogenic influence on increasing extreme sea levels via mean sea level contributions.”

On hurricanes and tropical storms: “Mean tropical cyclone maximum wind speed is likely to increase, although increases may not occur in all ocean basins. It is likely that the global frequency of tropical cyclones will either decrease or remain essentially unchanged.”

The scientists do not make recommendations on what, if anything, ought to be done in response. They only offer a “summary for policymakers.”

The report is dense, and it’s on a subject that provokes strong and opposing opinions. Definitions of basic terms have been negotiated. For instance, “likely” means at least a 66 percent probability that a conclusion is true, and “very likely” means at least a 90 percent probability.